For myself, the answer is prevention all together. Not saying I don't get them, but I try to reduce the chances of getting them, and then, perhaps lessen the severity of them.
Hydration has previously been stressed and I feel that is the overall main importance if your body is kicking out the sweat. Even in low humidity areas, your body may be dumping tons of fluids.
You can tackle this by start hydrating days- not hours before the dive. Simply chugging down a few power drinks before the dive is only filling your stomach up for filled dive. Lol. The others are spot on about reducing the caffeine and alcohol beverages prior to the dive. These are diuretics and will deplete your body of needed hydration. Besides perhaps preventing some cramps, proper hydration can also reduce the chances of decompression problems.
Besides proper exercise tuned for your leg muscles, nutritional support to some degree, and overall fitness what others haven't mentioned here yet is to learn some alternative kicks to give your leg muscles a break. Try some kicks such as the frog kick to see if you get some relief. There are several other types of kicks to use besides the standard scissor kicks and will only help you learn how to better enjoy your diving, and protect the areas by reducing some silting so that others can enjoy the same view as you.
Turtle and Jet fins are very good fins, and you will find that they are made for the diver to dive. You won't find a more simpler fin to use. Try not to get yourself caught up in the advertisement of Hollywood fins by falling for the bells and whistles they advertise. Fins are made to be a simple tool, not an investment!
Kenny